Like other polymeric materials, polymer foams are known to undergo degradation as a result of oxidation. The combination of heat, light, oxygen and other environmental oxidizing species can result in a decrease of polymer foam performance and integrity as the polymer chains become oxidized. Hence, manufacturers typically add antioxidizing agents and free radical inhibitors to preserve their products. Commonly, these antioxidizing agents are small-molecule additives which are not covalently hound within the polymer network.
To generate polymer foams, chemical or physical blowing agents are used. Chemical blowing agents are chemicals that take part in a reaction or decompose, giving off gaseous chemicals in the process. Physical blowing agents are gases that do not react chemically in the foaming process and are therefore inert to the polymer forming the matrix. Certain blowing agents such as chlorofluorocarbons (CFC's) have lost popularity as a result of their negative environmental impact.
In this invention, a method of polymer functionalization using 1,2,4,5-tetrazine has been developed which simultaneously, 1) generates polymer foams through a reaction which liberates nitrogen gas as an inert and environmentally friendly physical blowing agent and 2) modifies the polymer structure to give the materials antioxidant properties. The 1,2,4,5-tetrazine monomer is especially suitable for this application because of its cheap and easy synthesis, its solubility in unsaturated polymers and its lack of functional groups which could cause undesired polymer crosslinking. While many small molecules have low solubility in polymers and aromatic molecules such as tetrazines can also have limited solubility, the 1,2,4,5-tetrazine is soluble in some polymers (such as polybutadiene) and can even be reacted with some polymers without the addition of a solvent.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.